Fire Risk

Large buildings are designed very much like a ship; they are compartmentalised to prevent the spread of water. Similar compartments in a building are used to prevent the spread of fire. At regular intervals, physical barriers exist to prevent the spread of fire, including dampers and self-closing fire doors. This is to ensure effective containment of a fire. Through all these barriers must pass the air handling duct work. Because of the nature of the air-conditioning systems, they actually make an ideal conduit for fire. They are typically overhead where the greatest heat occurs from a fire, and as such, there must be a method of isolating them in the event of a fire.

The debris found in duct work is very often highly flammable. Dirty duct work allows the spread of fire simply by providing the fire with combustible material. The combination of dirty fire dampeners that do not shut and build up of dust and debris in the duct work can be devastating. "Duct Flash" can occur. This is where, fed by fresh air from the ducts and having material almost like powder to support combustion, the fire "flashes" through the duct work almost like an explosion. This can turn a controllable small fire, into a totally uncontrollable fire, before there is any chance of bringing the fire under control.